Catalytic converters are used to reduce or convert certain exhaust gas emissions from an internal combustion or turbine engine. One example of a catalytic converter involves a metallic housing, referred to as a can or mantle, into which is inserted a ceramic core. The ceramic core has a multiplicity of passageways or honeycomb structure defined by thin walls coated with the catalyst to provide the maximum contact possible between the catalyst and the exhaust gases flowing through the catalytic converter. In some catalytic converters, the relatively fragile ceramic core material is wrapped with a mat of fibrous packing material to help hold the core in place within the mantle, and to help protect the core from mechanical and thermal shock during handling of the catalytic converter and during operation of the vehicle or other equipment into which the catalytic converter is installed. Intumescent materials are also used as packing materials. One particular type of catalytic converter is a diminutive catalytic converter, which is especially suited for insertion into individual exhaust manifold ports, or for incorporation into small engine exhaust systems such as lawn mowers, chainsaws, mopeds, motorcycles and the like.
Once a combustion engine is started, typical catalytic converters require a short time interval for heat build-up to bring converter up to operational temperature. Meanwhile, the exhaust passing through the system is not properly treated. Due to ever stringent clean air standards being imposed on manufacturers of internal combustion engines, it is becoming more imperative to have the catalytic converter light-off (begin to function) earlier, as soon as possible after engine start-up in order to reduce this source of exhaust gas emissions. Manufacturers of these devices have attempted a number of means whereby catalytic converters may be quickly brought up to operational temperatures. Some methods involve preheating the catalyst and catalytic converter before engine start, while other approaches involve physically locating the catalytic converter closer to the exhaust manifold. Still other approaches involve insulating the exhaust pipe leading from the exhaust manifold to the catalytic converter. Each of these approaches has been found to be problematic.
One approach to this problem is to locate discrete catalytic converter elements wholly within either each exhaust manifold port or each exhaust port of the engine itself, or, partly within each part when the two parts are assembled together. This is generally considered to be a distributed approach with the small catalytic converters close-coupled to its heat source (cylinder exhaust for internal combustion engines), while the larger primary converter is remotely located. Such catalytic converters must be able to withstand the rigors of placement in close proximity to the engine and its associated severe operating environment. The extremes of high temperatures and exhaust pressure pulses can quickly destroy a catalyst substrate and/or its supporting mat rendering the catalytic converter inoperable if it is not properly supported within a metal can or mantle. It is important that the catalyst substrate exhibits a minimal amount of resistance to exhaust gas flow from the engine.
It would be advantageous if there could be developed improved inserts for catalytic converters that could be made in an economical manner. Also, it would be helpful if there could be developed a method and apparatus for making such catalytic converter inserts.